Process for manufacturing a hard bituminous composition with a curing agent



D. T. ROGERS ETAL 3,337,982 R MANUFACTURING A HARD BITUMINGUSCOMPOSITION WITH A CURING AGENT Filed March '7, 1965 June 11, 1968PROCESS FO O0.0 0.0 .O O.- O O www N-m. w Nmmmw w NmmmN wn- 0@ O l-mDlION n O D m3m 389m |o Ow Ommmlw .I O OO mNm OON OO Ow Ov ON O mm @Il O mD2 w w m 0 al' Inventors Potent Attorney Unite The present invention isconcerned with solid compositions stabilized with petroleum residua andwith a process of manufacture of these compositions and with shapedarticles of manufacture comprising these compositions. The invention isparticularly concerned with improved asphalt-stabilized soil andaggregate compositions having enhanced dry and Wet compressive strength,superior tensile and flexural strengths, and relatively low waterabsorption properties. The present invention is specifically concernedwith the use of curing agents to increase the compressive strength.

The present invention is a continuation-impart of Ser. No. 256,666,filed Feb. 6, i963, entitled, Improved Asphalt Solid Compositions andProcess of Manufacture, inventors Dilworth T. Rogers and lohn C. Munday,which, in turn, is a continuation-in-part of Ser. No. 178,038, tiledMar. 7, 1962, entitled, Stabilized Asphalt Solid Cornpositions andProcess of Manufacture, inventors Dilworth T. Rogers and John C. Monday.Both Ser. No. 256,666 and Ser. No. 178,638 are abandoned.

rlhe stabilization of soil and other solids employing petroleum bindersparticularly for use in the construction lield has not enjoyedappreciable commercial success. A very limited number of homes has beenbuilt, mainly in the western part of the United States, in which sandyclaytype soils in conjunction with asphalt have been used to formbuilding blocks. ln making these blocks, the asphalt was applied to thesoil as a water emulsion of an asphalt cutback solution in a naphtha.The mixture was then hand-tamped generally in wooden molds, and theblocks sun-cured for several weeks. The asphalt functioned mainly as a.Waterproofing agent rather than as a binder, since t .e asphaltincreased the wet strength of the soil but did not appreciably increasedry strength. ln this process, it was considered essential to wet thesoil with water before mixiig it with the asphalt outback, or to use anasphalt Water emulsion. The Water defiocculated the clay aggregate andserved as a compaction lubricant.

lt was found that building blocks produced by this prior art method andthe composition thereof gave maximum uncont'lned wet compressivestrengths at about 3 to 8 wt. percent asphalt, depending upon the typeof soil used, but failed to approach the compressive and tensilestrength of commercially available concrete blocks and brick. Despitetheir low unit strength, these materials were of some limited use inarid or semi-arid regions in the form of thick, solid blocks whereeconomic factors favored their use in certain types of construction.These blocks were wholly unsuitable in other geographical regions wherethere was a significant variation in humidity or where these buildingmaterials would contact moisture. Thus, beside very low compressive andtensile strength necessitoting the use of thick solid blocks foradequate strength, the prior art asphalt-stabilized soil compositionscould not be used in home construction, even in solid block form, wherethere was water contact or a variation in the humidity of the air,without a subsequent exterior coating. Thus, these prior art materialscould not be employed, for example, below grade or at footing levels. Afurther disadvantage of these prior art materials was the poor ad-States Patent O ICC hesion characteristics of exterior finishes such aspaint, mortar, stucco and the like to the exterior surface of theblocks. The blocks apparently expanded and contracted in response tosmall changes in the humidity of the air, resulting in extensivecracking and peeling of exterior coatings.

There has now been discovered a stabilized composition composed ofcritical quantities of subdivided solid and petroleum residua and aprocess for stabilizing solids, which composition and process avoid manyof the disadvantages of the prior art and provide, for example,asphaltstabilized aggregate and soil compositions of enhanced dry andwet compressive strength. ln accordance with a specic adaptation of thepresent invention, a critical quantity of asphalt is used in conjunctionwith soil of certain particlesize distribution and is compressed Withina critical range of its theoretical 100% density. The compressed solidis then heat-treated under specilic conditions to produce a high qualityproduct suitable as a building material such as blocks, bricks, tile,board, pipe and the like.

Thus, in accordance with the present invention 8 to 30% of asphalt byweight is mixed with the subdivided soid. The mixture is then compressedto a density of about to 98% based upon the theoretical density. Thecompressed product is then cured at a temperature in the range fromabout 300 to 500 F. for a time period of from about 4 to 80 hours. Thebinder employed in the present invention comprises that family ofmaterials cornmonly referred to as asphalts, such as natural orpetroleum residua of thermoplastic solid or semi-solid consistency atambient temperatures, normally of brown to black cementitious materialin which the predominating constituents are bitumens. The bituminousmaterial to be used may be selected from a wide variety of natural andindustrial products. For instance, various natural asphalts may be usedsuch as natural Trinidad, gilsonite, Grahamite and Cuban asphalts.Petroleum asphalts suitable for the purposes of this invention includethose asphalts obtained from California crude, from tar sands,Venezuelan or Mexican petroleum asphalt, or Middle East or a Mid-Continent airblown oil and the like, or combinations thereof. Petroleumasphalts also include those asphalts derived from hydrocarbon feedstocks such as bitumen, asphaltic residua obtained in a petroleumrefining process such as those obtained by the vacuum distillation of petroleum hydrocarbon crude oils, the solvent deasphalting of cruderesiduum fractions, tarry products from the chemical rening such asoxidation of high molecular weight hydrocarbons, those asphalts obtainedfrom hydrogenated coal products, the asphaltic material obtained in thethermal or catalytic cracking of petroleum to obtain gasoline or otherlight fractions or any combination of these materials.

Petroleum asphalts are generally prepared from petroleum residual oilsobtained by the distillation of an asphaltic or semi-asphaltic crude oilor thermal tar 0r by the uxing of harder residual asphalts with heavypetroleum distillates. Such residual oils are high boiling liquids orsemi-solids Which may have softening points from about 32 F. to about:120 F. and are generally characterized by specific gravities rangingfrom about 0.85 to about 1.07 at 77 F. Other properties of such residualoils, normally termed asphalt bases or asphalt lluxes, may vary to aconsiderable extent depending upon the particular crude oil from whichthey are derived.

Asphalts prepared from residual oils such as those set forth above .maybe classified as either straight reduced asphalts or as oxidizedasphalts. Straight reduced asphalts are produced by the steamdistillation, vacuum distillation, blending or solvent deasphalting ofresidual oils. These operations remove a significant quantity of thelower boiling, more volatile material present in the residual oils andresult in a product having a softening point between about 100 and about170 F., although higher softening points can be obtained by moreextensive treatment. Oxidized asphalts Iare produced by contacting aresidual oil with air or a similar oxidizing agent, alone or in thepresence of an 4oxidizing catalyst such as ferric chloride, phosphoruspentoxide or the like. The oxidation process serves to dehydrogenatecertainconstitueuts of the asphalt, leading to the evolution of waterand some carbon dioxide. Oily constituents are thus converted intoresins and resins are converted into asphaltenes. Very little oil isremoved during the oxidation operation. The penetration and ductilityproperties of oxidized asphalte are generally somewhat higher for agiven softening point than are those of the straight reduced products.Both straight reduced asphalts and oxidized asphalts are useful in theinvention.

Although the petroleum asphalts are preferred, other suitable bituminousmaterial would include coal tar, wood tar, and pitches from variousindustrial processes. The invention can also be successfully practicedwith chemically 4modified asphalts such as halogenated, e.g. chlorinatedor sulfurized or phosphosulfurized asphalts, as well as asphalts treatedwith epoxides or haloepoxides like ethylene -oxide and epichlorohydrin,or with silane halides, nitrobenzene, chlorinated alphatics such ascarbon tetrachloride and halohydrocarbons such as methylene chloride andthe like. Additionally, the asphalts can be mixed with minor amounts,e.g. l to l Wt. percent, of other natural and synthetic thermoplasticsand thermosetting materials like rubbers, resins, polymers andelastomers, of an oily, resinous or rubbery nature. Nonlimiting examplesof suitable materials include polyolefins, polypropylene, polyethylene,polyisobutylene, polymers from steam-cracked naphthas and the like;natural or synthetic rubber-like butyl rubber, halogenated butyl rubber,polydienes like p'olybutadiene, elastomeric copolymers of styrene andbutadiene, copolymers of ethylene and propylene and the like; epoxyresins; polyalkylene oxides; natural and synthetic waxes; polyvinylacetates; phenol aldehyde condensation products; and the like andcombinations thereof.

lFurthermore, in a modification wherein the asphalt is chemicallymodified by reaction with liquid reagents, for example, CCl4, thereagent liquid can often be used as the asphalt solvent, whereupon thedesired reaction occurs before, during or after the compaction of thesoilasphalt outback mixture, or during or after the curing step, or thereaction may occur continuously during both finishing process steps.

Satisfactory asphalts, for example, are those designated in the trade asiiuxes, binders, and various oxidized asphalts. Data on some typicalsuitable asphalts are shown below:

The solid material of .the stabilized compositions is any dry inorganicsolid material, with earth and soil the economically preferred solidmaterials for the production of hard dense structures useful in buildingconstruction. Suitable nonlimiting examples of other aggregate materialsinclude tinely subdivided cinder, expanded slag or clay, rock wool,steel wool, abrasives, coke from coal or petroleum, iron ore,diatomaceous earths, clays, soil, silt, coal, asbest-os, glass fibers,quartz, carbonate rocks, volcanic ash, and the like and any combinationthereof.

Thus, a wide variety of solids can be used in conjuncltion with theasphalt binder to form high strength strnctures. In general, mineralsare the preferred solids especially those which have well definedcrystal shapes and in particular those crystals which are readilycompacted to low voids-content structures. For example, kaolinite,chlorite, talc, mica, specular hematite which crystallize as plates ordiscs are readily compacted with asphalt to produce high strengthstructures. Asbestos, which has a fibrous structure and attapulgite,which crystallize as needles are less readily compacted.

As is well known, finely divided solids are more readily compacted togive nonporous structures than coarse. Clays and clay soils are examplesof finely divided. solids occurring in nature. -By the process of theinvention they can be used to prepare high strength structures. Alltypes of clay soils can be used, ranging from practically clay contentto those with l'ow clay content, if the structure will not be exposed towater. If the structure is to be exposed to water it is essential thatthe amount of the so-called expanding clays be kept at low levels, andgenerally below 10%, preferably below 5%. The expanding clays are thosewhich swell in the presence of water or other small polar molecules, andinclude the montmorillonites (bentonites), vermiculite, and open-endillite. Although these clays with l.asphalt have high dry strength theydisintegrate in the presence of water. For use in the presence of waterthe soil also should not contain appreciable amounts lof organicmatteror Watersoluble salts.

in order to waterproof clay soils with asphalt it is necessary to coverthe particles with a thin layer of asphalt. Since the surface area. offinely divided solids is high it is not unexpected that larger amountsof asphalt would be needed to provide a protective layer on highclay-content soils. For economic reasons therefore it is desirable touse relatively low clay content soils in asphalt-soil block manufacture.A very satisfactory soil is one which contains about 1Z0-25% clay, theremainder being silt and sand. With this soil 8-l2% asphalt by weight onthe soil will provide high strength and adequate water repellancy. ltwill be obvious that sandy, silty, and clayey soils can be blended toachieve the desired particle size distribution.

With some soils and minerals it is possible to obtain high strength withlittle or no clay or linelydivided particles (below 5p) present. Inthese, as mentioned previously, the coarse particles are present ascrystals of nearly equi-dimensional size (plates, discs, prisms, etc.)which are easily compacted to low void content structures. When thecoarser particles are not of this type, as found in sand and some silts,the strength of the asphalt soil blocks will be somewhat lower but maybe adequate for applications where high loads will not be applied suchas in onestory dwellings.

The particle size of soils is ordinarily determined by ASTM MethodD422-54T. In this procedure particle size is calculated from the rate ofsettling in a water suspension. Although clay soils form agglomeratesand aggregates of the primary soil particles they are largely broken upby water. It is thus possible to have a soil which appears to be verycoarse on the basis of a dry screen analysis but which shows a high claycontent in the ASTM D422-54T grain size analysis. On mixing the soilwith asphalt these agglomerates or aggregates are partially permeated byasphalt, and to some extent they are disintegrated into liner particleswhich are coated by asphalt. 'Coverage is not complete, however, and oneobtains a nonuniform structure which may have low strength and highwater sensitivity. It is essential therefore that the largeragglomerates be broken up by light grinding or other means approachingas a limit the same state of subdivision as indicated by ASTM D422-54Tbefore miX- ing with the asphalt.

Overall, soils in which kaolin is the chief clay constituent arepreferred for block making. Not only is kaolin of the proper crystalshape for easy compaction but it iS readily wetted by asphalt and theasphalt is not as easily displaced by water as with some other clays.There is some evidence that agglomerates and aggregates of kaolin arebroken up during simple mixing with asphalt and accordingly the amountof preliminary crushing is reduced and coverage is more complete.

FIGURE 1 shows the particle size distribution of various soils whichhave been used successfully in the process of the invention. It will benoted that clay content 0005 mm.) ranges up to 70%. Generally, desirablesoils contain from to 60% clay, with 20% to 40% clay preferred. Amongthe soils which have been found to be useful are Sayreville sandy clay,New Jersey red soil, Houston black clay, Lakeland ne sand, Ruston loamysand, Cecil coarse sandy loam, Cecil fine sandy loam, Marion loam,Neshorning silt loam, Chester si.t loam, Lakeland fine sand, Nigerianlatterite, Georgia kaolin, etc. Although the soils named above do notcontain much gravel (diameter more than 2 mm., equivalent to 10 mesh),soils containing gravel or to which gravel has been added can beemployed.

The asphalt can be incorporated with the subdivided solid material as asolvent cutback, using a volatile organic cutback solvent such aspetroleum naphtha or other solvent boiling in the range of about 175 F.to 600 F., e.g. 200 F. to 400 F. The outback solvent should preferablybe one that is sujticientiy volatie to be substantially volatilizedduring the selected curing step, i.e., a solvent having a boiling pointof less than 600 F. or advantageously less than 400 F. Suitable asphaltconcentrations in the outback solution are from 30 to 90 wt. percentasphalt, eg. 50 to 75%. Preferably, the Furol viscosity at thetemperature at which the cutback is applied should be i00 or less, e.g.20 to 100 Furol. Suitable cuback solvents thus include, but are notlimited to, hydrocarbons sucn as toluene, benzene, xylene, varsol, VM&Pnaphtha, halohydrocarbons such as carbon tetrachloride and methylenedichloride, or any combinations thereof. Whatever the solvent, it shouldbe substantially removed from the asphalt-solid mixture prior tocompaction, as disclosed in the parent application, Ser. No. 178,038.

The asphalt can also be incorporated with the subdivided solid while inthe molten state and this is generally the preferred method. Thetemperature of the asphalt at the time of mixing should be such that theviscosity is suiciently low that good mixing is achieved and the solidparticles are uniformly coated. Suitable asphalt viscosities are in therange of about 20 to 100 Furol, corresponding to mixing temperaturesfrom about 275 F. in the case of soft asphalts such as uxes, to 350-450F. in the case of harder asphalts such as binders and oxidized asphalts.In carrying out the hot-mixing operation, the solid is generallypre-heated and charged to the mixer, and the molten asphalt is thenpumped in. It iS usually suicient to introduce the asphalt as a lowpressure spray, although atomized or foamed asphalt can be used. Variouscommercial mixers are suitable, such as the type of paddle mill known asa pug mill. Where an eicient mixer is employed, the time of mixing canbe relatively short, such as one or two minutes. In some cases, however,it may be desirable to extend the mixing time to say -30 minutes orlonger in order to harden the asphalt after incorporation with thesolid. For example, it has been found that when starting with flux orbinder asphalts, stronger structural products are obtained if theasphalt is hardened in this fashion by heating in air, say at 400 F.,after mixing with the solid, but before compacting the mixture.Conversely, when starting with a hard asphalt such as an air-blownasphalt, it may be desirable to blanket the mixer with inert gas so ast0 decrease the rate of hardening.

Generally, it is preferable to mix the asphalt cutback or the moltenasphalt with solid that is relatively dry, having not more than l-2%moisture. When solid containing considerable Water is employed, it ispreferable to dry the solid-asphalt mixture to a fairly low watercontent prior to compaction. If this precaution is observed, emulsiedasphalt cutbacks can be employed in the process of the invention. Theamount of asphalt employed is in the range from about 8% to 30% byweight, based on the solid. Generally, the amount employed is in therange from about 10% to 20%.

The development of high strength materials from iinely divided solidsand residua (asphalts) depends to a marl-:ed extent on high temperaturecuring, e.g. 300#500 F. The time of curing depends on the temperaturelevel, the higher the temperature the shorter the time needed. Ingeneral, the curing conditions to produce blocks which retain theirstrength in the presence of water and which do not absorb water `areless severe than those required to produce high dry strength.

The principal mechanism involved in the formation of high strengthmaterials from solids and asphalt appears to be oxidation of the asphaltalthough the evolution of volatile material is also involved to someextent. The volatile material may be present in the original asphalt orsubsequently produced by cracking and oxidation.

That oxidation is the chief mechanism is shown by comparing the resultsof curing in air versus nitrogen. In the latter case, with clay soil andasphalt, the compressive strength was less than one-half of those curedin air.

To develop high strength during curing, the compacted solid-asphaltstructure should have sufficient porosity to permit the diffusion ofoxygen into the interior of the structure and to permit the egress ofvolatile materials without disrupting the binder (asphalt) films. Thesolid particles however must be sufficiently close together so that thegreater part of the binder is present as a very thin, nearly-continuousphase if high strength is to be developed on curing. Thus if there isinsufficient binder to cover most of the soiid particles with `very thinfilms and if cornpaction is not carried to the point where the solidsare brought in close proximity, low strength, especially in the presenceof water, will result. On the other hand, if an excess of `asphalt ispresent, thick lms will be formed and low strength will result oncuring, regardless of the degree of comp-action. At low densities thestrength of the structure would not be expected to be much greater thanthat of asphalt by itself. At high densities diffusion of oxygen intothe interior of the structure and even into the interior of the thickbinder films is retarded and more significantly the evolution ofvolatile materials is impeded. The latter effect results in severecracking during curing and produces both deformation `and low strength.

In order to designate a suitable range of density (degree of compaction)for the development of high strength an expression Percent ofTheoretical Density has been formulated which is defined `as follows:

Percent of Theoretical Density=percent of the density the solid-f-binderwould have if there were no voids in the compacted structure.

A sample calculation would be: A compacted mixtur of clay soil (d.=2.6lg./cc.) with 10 wt. percent asphalt based on the soil (d.=l.04 g./cc.)is found to have a density of 2.08 g./cc. The theoretical density (novoids) of this mixture would be With sandy clay soils containing about20-25% clay and 942% by weight asphalt, the desired percentage oftheoretical density is usually within the range 88 `to 98%, the exactlevel depending upon factors such as the concentration of asphalt,curing conditions, yand the size and shape of the article being molded.

To achieve the advantages of the invention, the asphaltsolid mixtureshould be compacted to a density in the range from about -98% of thetheoretical density, a

more preferred range being from about 21S-95%. In many cases, maximumstrength is developed in a still narrower range, such as S8-92%. Theoptimum percent theoretical density varies with a number of factors,such as asphalt concentration, compaction temperature, presence ofsolvent at the time of compaction, curing conditions, and lthe size andshape of the `article being molded. For example, with sandy clay soilscontaining about 20-25% clay and 10-12 wt. percent asphalt, the optimumdensity is usually inthe range from about 88-94% theoretical density,while with 9% asphalt the optimum may be higher, such as about 96%. lso,Whereas the optimum may be about 92% in the case of 1.28 diameter X 3"high briquettes, it may be about 88% in the case of 8 x 4" X 2.5 bricks.Suitable compaction temperatures are from 50 to 350 F., preferably from60 to 200 F.

In accordance with a specific adaptation of the present invention, solidcompositions of enhanced strength are produced by utilizing la curingagent selected from the class consisting of nitrobenzene,dinitrobenzene, gallic acid, pyrogallol and furfural. These agents areused in a concentration of from about 0.5 to preferably in aconcentration of 1 to 2% by weight based on the soil. The materials alsoare preferably mixed when the asphalt and soil are mixed.

The present invention may be more fully understood by the followingexamples illustrating embodiments of the same.

Example 1 A. New Jersey sandy clay soil, referred to as Sayreville-Roxburgh mixture (SR No. 1), was mixed with 12% (by weight based on thesoil) of an oxidized asphalt which had a softening point of 213 F. Theasphalt was applied as a 50/50 cutback in toluene at 75 F. Agitation wasprovided by a Hobart mixer. The toluene was allowed to evaporatecompletely while the mixture was being agitated. Varying amounts ofnitrobenzene were added and the mixture was then compacted intocylindrical briquettes (1.28 in diameter x 3" (approx.)) under apressure of 2340 p.s.i. for 5 minutes. The briquettes were then cured inan electric oven -for 16 hours at 350 F. As shown by the data in Table Ithe nitrobenzene serves two functions. It facilitates compaction andincreases the strength of the cured briquettes. With this particularsoil-asphalt combination, compaction pressure and curing conditions itappears that the optimum concentration of nitrobenzene is approximately1-2 Wt. percent based on the soil. It will be noted further that whenthe briquettcs are compacted to high density (98% of theoretical) in theabsence of nitrobenzene, low strength results.

TABLE 1.--NITROBENZENE As Il COMPACTING AND CURNG AGENT ['NJ. Sandy Clay(SR No. l) plus 12% 213 S.P. Oxidized Asphaltcompacted at 75 F.,2,3-10psi., 5 1nin.]

1 After immersion in water or days at 75 F. 2 Developed cracks duringcurnig. S Compactcd at 6,253 p.s.1.

Example 2 Briquettes were prepared as in Example l except that a ISN/200S.P. oxidized asphalt was used in place of the 213 S.P. oxidizedasphalt. As shown by the data in Table Il the addition ot' nitrobenzeneto theasphaltsoil mixture markedly increased the density on compactionand also resulted in increased strength.

TABLE II.NITROBENZENE AS A C URING AGEN gOMPACTIN G AND Percent olCompressive Strength, 5 Wt. percent Nitrobenzene Theoretical p.s.i.

(on Soil) Density Dry Wet 10 l Seine cracks developed during curing.

Example 3 Briquettes were prepared as in Example l except that a verysoft asphalt, Flux A, was substituted for the 213 S.P. oxidized asphalt.As -found in the previous examples the inclusion of nitrobenzenelfacilitates compaction and increases strength. Data are given in TableIII.

TABLE IIL-NITROBENZENE AS A COMPACTING AND CURING AGENT INJ. sandy snNo. 1) plus 12% rim A] Percent cf Comprcssive Strength, Wt. percentNitrobenzcne Theoretical p.s.i.

(cn Soil) Density Dry Wet 94. 2 2, 91e 2, ao es. 3 3, 295 2, 305 97. 02, sse 2,160 99.0 2,085

Example 4 Briquettes were prepared according to the method of Example 1,but a bindergrade asphalt (Binder C-Pcn. 77 F. of 80) was used in placeof the oxidized asphalt. With this asphalt the addition of nitrobenzencwhile in' creasing the density during compaction decreased the drycompressive strength. The wet compressive strength was increasedsomewhat however. See Table IV.

TABLE IV.-NITROBENZENE AS A COMPACTING AND CURING AGENT Briquettes wereprepared as in Example 1 except that Binder C was used as the asphalt.Also the Binder C was applied at 350 F. without solvent, thesoil-asphalt mixture was heated for one hour before compaction and thencompacted at 350 F. When nitrobenzcne was included in the composition itwas added during the iinal stage of the mixing operation. As shown bythe data in Table V moderate increases in density and strength wereobtained with 1% nitrobenzene. With 4% nitrobenzene the briquettes wereover compacted, and cracks developed during curing.

TABLE v.-NITnoBENznNE as A COMPACTING AND CURIN G AID INJ. Sandy Clay(SR No. 1) plus 12% Binder C] Percent ol Compressive Strength, Wt.percent Nitrobenzcnc Theoretical p.s.i.

(on Soil) Density Dry Wet 94. El 3, 775 2, 880 e5. 3 b, 815 2, eso 100.0 l 3, 865 l 2, S00

l Cracks developed during curing.

Example 6 Briquettes were prepared and tested. as in Example 1 with thefollowing exceptions. The toluene was not completely evaporated prior tocompaction-1.5 wt. percent 5 (on soil) remaining. Curing was carried outin a heated- CDO 9 air type oven in which a large volume of heated airwas being circulated. A slightly different soil was also used, NewJersey Loose Sandy Clay (SLS-3) which contained slightly less clay. Asshown by the data in Table V1 both nitrobenzene and dinitrobenzenemarkedly increase cornpressive strength.

TABLE VI.-NITROAROMATICS AS CUEING AGENTS INJ. SLS-3 Soil plus 12% 213Oxidized Asphalt plus 1.5 Wt. percent olueue] Unconfmed CompressiveAdditive Wt. percent Strength, p.s.i.

Dry Wet None 3, 680 2, 735 Nitrobenzene. 1.0 4, 525 260m-Diuitrobenzene 1. 4, 345 3, 410

Example 7 Briquettes were prepared as in Example 1 except that threedifferent soils were `used in place of the New Jersey Sandy Clay soil.These were Iowa Loess, adobe gravel (Arizona) and a Wyoming bentonite(Eig Horn Clay Company). As shown by the data in Table V11, theinclusion of nitrobenzene increased the wet strength of the adobe andIowa Loess briquettes but although it markedly increased the drystrength of the bentonite briquette, the wet strength was not improved.

TABLE V1I.-N1TROBENZENE AS A CURING AGENT [Diierent Soils 213 Sl.Oxidized Asphalt] [SR No. 1 plus 12% Thus, there are several advantagesin the use of the nitrocompound. Because of the strong plasticizingpower of nitrocompounds especially nitrobenzene and other aromaticnitrocompounds, for asphalt it is possible to employ harder asphalts.Since the harder asphalts require less oxidation, curing is necessarilyless drastic (lower temperatures and shorter time). When starting withhard asphalts there is less volatile material which must escape duringcuring and also a lesser amount of volatile oxida- 0 tion products, bothof which tend to disrupt and weaken the 'binder lm. Also the oxidizingagent is uniformly distributed throughout the structure and more uniformcuring results than when air alone is the oxidizing agent since the rateof curing in the interior of the structure is limited by the rate ofdiffusion of oxygen. Thus by employing nitrooompounds one can employhard asphalte, can compact to higher densities which will withstandcuring without cracking and strong, water resistant structures result.

What is claimed is:

1. A process for the manufacture of a hard bituminous solid compositionwhich comprises mixing from about 8 to 30 wt. percent of a bituminousbinder, 0.5 to 5 wt. percent of a curing agent selected from the groupconsisting of nitrobenzene, dinitrobenzene, gallic acid, pyrogallol andfurfural with iinely divided solid, by weight percents based on thesolid, compressing the mixture to to 98% of its theoretical density andcuring the compressed mixture at a temperature in the range from about30 to 500 F. for a time period in a range from about 4 to '80 hours.

2. Process as deiined by claim 1 wherein the curing temperature is inthe range from 350 to 450 F.

3. Process as dened by claim 2 wherein the time period for curing is inthe range from about 8 to 24 hours.

4. A process as defined by claim 1 wherein the amount of binder presentis in the range from about 10 to 20 wt. percent, wherein the mixture iscompressed to to of the theoretical density of the s-olid composition.

5. Process as defined by claim 4 wherein said soil contains from about10 to 60% of clay.

213 8.1. Ox. Asphalt-Compaction: 2,340 psi., 1.5% Toluene (ou soil).Curing: 16 hrs. at 350 F., ConvectionJlype Oven] Weight Percent oConipressive No Additive percent Density, Theor. Strength, p.s.i.

(on Soil) glee. Density Dry Wet 2. 09 94. 0 3. 680 2, 735 2.07 93.4 4,525 3,260 2. O8 94. 0 4, 680 3, 175 2. 08 94. 0 4, 390 2, 975 2. 06 93.O 4, 345 3. 410 2. 09 94. 0 4, 095 3, 080 2. 06 93. 0 3, 540 2, 890 2.1395. 6 3, 530 2, 270 2. 01 90. 3 3, 00 1, 950 2.11 95. 0 3,040 2, 720 1..98 89.2 2, 040 1. 745 2. 06 94. 5 2, 840 2, 540 Paranox 44l. 2.12 95.32,775 2, 300 Pheuothiazine 2. 08 93. 6 2, 040 2, 410

References Cited UNITED STATES PATENTS 1,966,094 7/1934 Herbst 106-2802,500,209 3/1950 Shea et al 106-280 X 2,917,395 12/1959 Csanyi 106-283 X3,261,892 7/1966 Sommer et al. 264-29 3,168,602 2/1961 Davis et al.264-29 3,287,146 11/1966 Rogers et al. 324-75 2,764,523 9/ 1956 Cottleet al 208-44 XR 2,992,935 7/ 1951 Winslow 208-44 XR 3,275,585 9/1966Baum et al. 208-44 XR JAMES A. SEIDLECK, Primary Examiner.

I. B. EVANS, Assistant Examiner.

1. A PROCESS FOR THE MANUFACTURE OF A HARD BITUMINOUS SOLID COMPOSITIONWHICH COMPRISES MIXING FROM ABOUT 8 TO 30 WTY. PERCENT OF A BITUMINOUSBINDER, 0.5 TO 5 WT. PERCENT OF A CURING AGENT SELECTED FROM THE GROUPCONSISTING OF NITROBENZENE, DINITROBENZENE, GALLIC ACID, PYROGALLOL ANDFURFURAL WITH FINELY DIVIDED SOLID, BY WEIGHT PERCENTS BASED ON THESOLID, COMPRESSING THE MIXTURE TO 80 TO 98% OF ITS THEORETICAL DENSITYAND CURING THE COMPRESSED MIXTURE AT A TEMPERATURE IN THE RANGE FROMABOUT 30* TO 500*F. FOR A TIME PERIOD IN A RANGE FROM ABOUT 4 TO 80HOURS.